Field of the Invention
The present invention relates to a trocar for bone marrow biopsy, and to a device for bone marrow biopsy that connects a trocar to a motorized rotational drive means.
Description of Related Art
The techniques for performing bone marrow biopsies are the fine-needle biopsies by puncture and aspiration of the marrow (myelogram) and the osteo-medullary biopsies for collecting samples of the marrow and the medullary stroma, the choice being dependent on the result sought by the practitioner (cytology or histology).
Biopsy by aspiration can be performed using a fine needle with a 15-16 gauge, for example. By contrast, if the desired result is of a histological nature, use will preferably be made of the osteo-medullary trocars with a greater diameter (13 gauge for example), thereby allowing a larger sample to be collected.
Traditionally, bone marrow biopsies of the osteo-medullary type are performed especially in the crest of the iliac bone where there is fine cortical bone substance. To perform these biopsies, the procedures presently carried out are either manual or motorized. The manual procedures have certain disadvantages, the main ones being associated with the penetration into the cortical bone and with the recovery of the sample. Most of the needles used manually have simple mandrels with a trocar tip that is not especially sharp, thus forcing the practitioner to exert considerable pressure during the penetration into the bone. The procedure may therefore prove particularly awkward and may cause pain and discomfort for the patient. Once the cortical bone substance has been penetrated and the mandrel withdrawn, the needle is driven into the bone by several millimeters (10 to 30 mm) in order to recover a sample of marrow and medullary stroma. Before the withdrawal of the needle, and in order to ensure that the tissue sample is maintained in the needle, it is recommended to tilt the needle to and fro slightly and rotate it. This manoeuvre makes it possible to cut the specimen and contributes to the successful recovery of the sample. However, it is particularly painful for the patient.
The motorized procedures significantly attenuate the difficulties of penetration and sampling and are less painful for the patient; they also make it possible to reduce the length of time it takes the practitioner to perform the procedure.
U.S. Pat. No. 6,019,776 discloses an access trocar used in particular in vertebroplasty for injection of materials, comprising a cannula and a stylet, the stylet being guided in the cannula. The cannula and the stylet have threads which allow the cannula to be positioned on the stylet and to advance to a predetermined position. The stylet also has a bone-drilling thread at its distal end. The thread of the cannula is not suitable for retaining a marrow sample since it is too far from the distal end of the cannula.
U.S. Pat. No. 6,086,543 describes a biopsy trocar for soft tissues. The cannula of the trocar has, at its distal end, a thread for retaining the tissues during the withdrawal of the cannula.
U.S. Pat. No. 7,988,643 describes a biopsy trocar for manual use which, on the distal end of the needle, has an internal thread and external thread, and also a conical part. This needle is connected to a handle. This device has the major disadvantage of having an external thread which, on account of the bone density, will be very difficult to remove without having to unscrew it, which will not allow the marrow sample to be withdrawn correctly.
U.S. Pat. No. 6,110,128 describes a biopsy trocar for manual use, characterized in that the needle has internal ribs inclined towards the rear. This device will not permit bone marrow biopsies of good quality, since the ribs will oppose the penetration of the marrow into the needle. The reason is that, since the trocar is used manually, the speed of rotation is not fast enough to drive the marrow into the needle. In addition, the formation of ribs as described in the patent is technically complicated and very costly.
U.S. Pat. No. 7,850,620 describes a trocar for motorized use, having a needle with a helical thread portion that is welded inside the distal end, making it easier for the marrow to enter the needle during the biopsy, and a mandrel whose distal end is ground to a pyramidal point. This trocar has several disadvantages. Since the external diameter of the mandrel is less than the internal diameter of the thread crest, there is quite significant play between the external diameter of the mandrel and the internal diameter of the needle. This play may cause accidental attachment and therefore tearing of the soft tissue parts during the introduction of the trocar, but also clogging with bone debris during the perforation of the cortical bone. This clogging may cause difficulties when removing the mandrel from the needle, since the mandrel remains affixed to the internal wall of the needle. It may also cause accidental entry of debris between the mandrel and the internal wall of the needle, thus creating a coating of the internal wall, of which the thickness may be equal to the height of the crest of the welded thread. The efficacy of the system for recovering the specimen, and therefore of the welded thread, is then compromised since the welded thread is in fact embedded within the thickness of the coating and becomes ineffective for the following step of performing the biopsy proper. Finally, the formation of such a thread by welding is technically difficult and particularly costly. Of course, the difficulty increases significantly as the size of the needles decreases.
These trocars make it possible to perform bone marrow biopsies, but, in the case of the manual devices, with longer and more painful operating techniques and, in the case of the motorized device, with risks of failure due to clogging.